Silverstone is currently undergoing a renovation not just to the facilities around the track but the track layout itself. The new layout is called the Arena layout and was probably designed to cater to the MotoGP and Superbike races but was considered for F1 as well.
It seems that this year F1 might use the new layout, I say might because it has not received approval yet from all parties concerned. The last party to give consent is Bernie (of course). More in-depth story can be found at F1Fanatic where Keith gives the run down on what is happening with pictures and a layout map.
What do I think of the new layout? It looks interesting, not much of a radical change and maintains the high speed nature of Silverstone - which is good. This new layout is probably designed more for the fans than the drivers anyway.